Put this shell function into your .bashrc, set LESSPATH=/var/log/user and now you can run less as you want to.

You can add other paths to LESSPATH by separating them with colons, just like the other PATH environment variables. So, if you set LESSPATH=/var/log:/var/log/user, you could also easily run less syslog from anywhere to easily see /var/log/syslog.